| Research Abstract |
AP12-MALT1 fusion gene is specific to mucosa-associated lymphoid tissue (MALT) lymphoma. We recently described a multiplex RT-PCR assay for this fission gene that can be applicable to paraffin sections. Using this assay, we clarified clinicopathological significances in MALT lymphomas of the lung, skin, ocular adnexa, colon, and stomach. The fusion gene was detected in 41% of pulmonary MALT lymphoma cases. The patients with fusion gene-positive tumors rarely had autoimmune disease, and their LDH level was often normal. Histologically the fusion-positive tumors were typical for MALT lymphoma, and were associated with nuclear BCL10 expression (Am J Pathol, 2003). Twenty-four Asian cases of cutaneous MALT lymphomas were negative for API2-MALT1 fusion and Borrelia infection. However, nuclear BCL10 expression, which is closely associated with the fusion gene, was frequently detected in the tumor calls, and was associated with macroscopically nodular lesion (Am J Surg Pathol, 2003). MALT lym
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phoma of the ocular adnexa showed the API2-MALT1 fusion in 13% of the cases analyzed. These positive cases often showed other chromosomal abnormalities, suggesting that some cases of the fusion-positive ocular MALT lymphoma might progress to high-grade lymphoma (Mod Pathol, 2003). MALT lymphoma of the colon showed the API2-MALT1 fusion in 15% of the cases analyzed. The fusion gene was often found in male patients, and was associated with advanced clinical stage. The latter observation suggests that a close follow-up may be needed for fusion-positive MALT lymphomas of the colon (Mod Pathol, 2003). An analysis of gastric MALT lymphomas involving multiple organs showed that these cases were frequently positive for API2-MALT1 fusion, negative for H. pylon infection, and resistant to H. pylori eradication therapy (J Gastroenterol, 2004). A large-scale analysis of gastric MALT lymphoma showed that API2-MALT1 fusion-positive tumors were totally resistant to H. pylori eradication therapy. Consequently, we divided gastric MALT lymphomas into three groups: (A) eradication-sensitive, (B) eradication-resistant, fusion gene-negative, and (C) eradication-resistant, fusion gene-positive. Each group showed unique clinicopathological features (Am J Surg Pathol, 2004). An API2-MALT1 fusion-negative pulmonary MALT lymphoma case which was developed in a HIV negative young man was reported (Leuk Lymphoma, 2004). Less
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